I have a 1996 XJ 4.0. I recently did my own coolant flush and put a new thermostat and mixing valve in along with thermostat housing. I seemed to have gotten air in the system so I brought it in to get a real coolant flush. It has been incredibly cold here in Minnesota lately but even before that the heat wasnt keeping up very good. Both before and after the flush and new parts my temp gauge only gets up to 1/4 on the dash, im not sure if this is normal or not? I put a 180 or 185 stat in which is what was previously in there. Now when i drive down the road or rev the engine it will blow warm/hot air out but when I come to a stop light it blows cold/luke warm air. I havent tried flushing or replacing the heater core yet. do these symptoms seem like they are heater core related or something else?

 

Reverse flush heater core. Replace thermostat with Mopar 195*, which was original.

I would recover as much of the coolant as possible, since it is new.

 

Thanks man, ill give that a shot

 

That should do it, unless your water pump vanes are about gone.

Low coolant circulation at idle through heater core.

 

Water pump was also replaced a few years back...

 

Also I'm curious where the temp gauge should sit? I'm assuming just under 1/2?

 

Yeah, that's about right. But in very cold weather, it could be lower.

You can verify actual temp with an IR gun aimed at the thermostat housing when fully warmed up.

 

True. However, my experience with the IR gun is, that temps are all over the place, even on the thermostat housing and measured from close distance....mixed feelings about that.

 

Thanks for the help guys, I'll give it a shot!

How difficult is the heater core to change if that's the case?

 

Thats a bit of a hassle. Try the hose flushing first.

 

Also, don't shy away from eliminating the heater control valve with a piece of tubing and plugging the vacuum line.

 

Actually, I have to admit I've not had personal experience with an IR gun. It was a suggestion I have seen from time to time by others.

 

You Aussies certainly have a talent for understatement.

 

I think their readings can be skewed by the reflectivity of certain things like shiny aluminum pieces.

 

No worries....